MOOC 实现二分查找算法（基于顺序表）

Posted 2021-02-10 zjsaipplp

#include <stdio.h>
#include <stdlib.h>
#define MAXSIZE 10
#define NotFound 0
typedef int ElementType;
typedef int Position;
typedef struct LNode *List;
struct LNode {
    ElementType Data[MAXSIZE];
    Position Last; /* 保存线性表中最后一个元素的位置 */
};
List ReadInput(); /* 裁判实现，细节不表。元素从下标1开始存储 */
Position BinarySearch( List L, ElementType X );
int main()
{
    List L;
    ElementType X;
    Position P;
    L = ReadInput();
    scanf("%d", &X);
    P = BinarySearch( L, X );
    printf("%d
", P);
    return 0;
}

/* 你的代码将被嵌在这里 */
List ReadInput(){
    List PtrL;
      int N;
      scanf("%d", &N);
      for(int i = 1; i <= N; i++){
        scanf("%d",&PtrL->Data[i]);
      }
      PtrL->Last = N;
      return PtrL;
}
Position BinarySearch( List L, ElementType X ){
    int Left = 1, Right = L->Last, mid;
    while(Right - Left >= 0 ){
        mid = (Left + Right) / 2;
        if(L->Data[mid] > X){
            Right = mid - 1;
        }else if(L->Data[mid] == X){
            return mid;
        }else{
            Left = mid + 1;
        }
    }
    return NotFound;
}